This invention is related to a patient access device and particularly to one which permits the introduction of an external filament such as a needle, external catheter, guide wire, or optical fiber transcutaneously.
This invention relates to a device to enable multiple patient access procedures including infusing a therapeutic agent to a desired site within a patient, feeding a filament to a desired internal site, or withdrawing a fluid from a patient; and more particularly, to such a device which is implanted such that no portion is transcutaneous. Its access portion is subcutaneous but designed so as to facilitate repeated access by the percutaneous route.
In current human and animal medical practice, there are numerous instances where therapeutic agents must be delivered to a specific organ or tissue within the body. An example is the infusion of chemotherapy into a central vein on a recurring basis over a lengthy treatment period for widespread sites of malignant tumor. Without an access device for intravenous drug infusion, multiple vein punctures over a lengthy period can result in progressive thrombosis, venous sclerosis, and destruction of small diameter peripheral vessels. In other cases, it may be desirable to infuse chemotherapy to a localized malignant tumor site. It may be difficult or impossible to deliver an agent specifically to such a site on a regular repetitive basis without surgically implanting an access system. Similarly, repeated arterial access is occasionally needed for injection of an X-ray dye or contrast agent into an artery for diagnostic purposes. In other situations, there is a need to remove a body fluid from a remote body site repetitively for analysis. Finally, sensing and physiological measuring devices incorporated into small diameter catheters and small diameter optical fibers are increasingly being utilized for monitoring body processes and could be more easily implemented through a properly designed access device with an adequate internal diameter.
In prior medical practice, percutaneous catheters have been used to provide vascular or organ access for drug therapy or removing body fluids. Although such systems generally performed in a satisfactory manner, numerous problems were presented by such therapy approaches, including the substantial care requirements by patients, e.g. dressing changes with sterile techniques, a significant rate of infection of the catheter because of its transcutaneous position, and a high rate of venous thrombosis, particularly if the catheter was located within an extremity vein.
Implantable infusion devices or "ports" have recently become available and are a significant advance over transcutaneous catheters. Presently available infusion ports have a number of common fundamental design features. The ports themselves comprise a housing which forms a reservoir which can be constructed from a variety of plastic or metal materials. A surface of the reservoir is enclosed by a high-density, self-sealing septum, typically made of silicone rubber. Connected to the port housing is an outflow catheter which communicates with a vein or other site within the patient where it is desired to infuse therapeutic agents. Implantation of such devices generally proceeds by making a small subcutaneous pocket in the patient under local anesthesia. The internal outflow catheter is tunnelled to the desired infusion site and is connected to the infusion port. When the physician desires to infuse or remove material through the port, a hypodermic needle is used which pierces the skin over the infusion port and is placed into the port.
Although presently available implantable infusion ports generally operate in a satisfactory manner, they have a number of shortcomings. Since these devices rely on a compressed rubber septum for sealing, there are limitations in the diameter of needles which can be used to penetrate the septum, since large diameter needles can seriously damage the septum. These diameter limitations severely restrict the flow rate of fluids passing through the port. Moreover, the needles used must be of a special design which minimizes septum damage.
For prolonged infusion using a conventional port, the infusion needle is taped to the patient's skin to hold it in position. Conventional ports do not allow the needle to penetrate deeply into the port; and consequently, a small displacement of the needle can cause it to be pulled from the port, allowing extravasation. In cases where locally toxic materials are being infused, extravasation of such materials can cause local tissue damage which can lead to a requirement for corrective surgery such as skin grafting or removal of tissue.
Presently available implantable infusion devices must also have a significant size to provide an acceptable target surface area for the physician who must locate the port and penetrate the septum properly with a needle. The port housing becomes bulky as the septum size increases since structure is required to maintain the septum in compression to provide self-sealing after the needle is removed. Moreover, presently available infusion ports are difficult to clear if thrombosis occurs within them or in the implanted outflow catheter, since it is difficult if not impossible to feed a cleaning wire through the penetrating hypodermic needle in a manner which will clear the infusion device and the internal outflow catheter. Present infusion ports have a space which contains a retained fluid volume beneath the self-sealing septum which increases the volume of drug which must be administered to enable a desired quantity to reach the infusion site. This retained volume also poses problems when a physician desires to deliver different drugs to the same infusion site which are incompatible or rendered less effective when mixed. In addition, when it is desired to withdraw blood through the port, the retained volume of the prior art infusion ports is an area where blood clotting can occur, thus interfering with future access to the site. And finally, for present infusion ports, there is a risk that the physician attempting to pierce the port septum will not properly enter it, leading to the possibility of extravasation which can cause significant undesirable consequences as mentioned previously.
In applicants' related patent application and issued patents, various approaches toward permitting transcutaneous access to implanted catheter are described. In accordance with those devices, multiple sealing members are used to provide an adequate fluid seal across the access device, both when an external filament is introduced into the device and after it is removed. The access ports in accordance with this invention achieve simplicity in construction and reduce the number of components necessary to provide the necessary fluid seal. In those applications where it is desired to access a port using a sharp needle, damage to elastomeric sealing elements can occur over repeated entries to the port in prior port designs. In accordance with this invention, the implanted port has an articulating valve mechanism in which the accessing needle (or other filament) contacts a hard material such as a metal to open the valve. Accordingly, a durable device is provided which is not damaged through long term use.
The features of the present invention are primarily achieved through use of a valve assembly in which a sealing element is normally maintained in contact with a valve seat. When introducing an external filament, which may be a needle, catheter, wire, optical fiber etc., the filament engages the sealing element forcing it from engagement with the valve seat. Once fully inserted into the access device, features are provided to assure a fluid seal around the introduced filament.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.